I think it was quite often the case that in the UK a RHD vehicle was worth more but to me it seems that is becoming less important as classic car values rise, and I wonder if the internet has had some effect in that a lot of cars advertised in the UK find their way into Europe and so LHD is more beneficial.
It has never bothered me either way if a car is RHD or LHD, and personally I wouldn't pay more for a RHD car in the same condition. We get a few enquiries a year asking about converting Corvettes to RHD, something I have little or no interest in doing, and funnily enough the few that I have seen done and that come up for sale really bomb in value over here.
The only time a LHD car is a pain in the UK is when going in to multi story car parks, even then most times you can reach across or get out and walk round. The roads in this country are too small and crowded to overtake any more so you don't even need to see past anything....
My SL is LHD but that wasn't even a factor when I bought it, never even gave it a second thought.